The present invention relates to a blade element for a refiner for refining fibrous material, the blade element comprising a blade element body and blade bars and blade grooves therebetween, the blade bars and the blade grooves providing a refining surface of the blade element, and in which blade element bottoms of the blade grooves have, in the longitudinal direction of the blade grooves, a variable profile comprising alternating high points and low points.
The present invention also relates to a refiner for refining fibrous material, the refiner comprising opposing refining elements, each of which comprises at least one blade element provided with blade bars and blade grooves therebetween.
The present invention also relates to a method for manufacturing a blade element for a refiner for refining fibrous material, the method comprising manufacturing a blade element billet comprising a blade element body and protrusions and recesses therebetween for providing blade bar billets and blade groove billets therebetween.
Refiners intended for refining fibrous, lignocellulose-containing material are employed, for instance, for producing pulp to be used in paper or board manufacturing. Conventionally, these refiners comprise two opposing refining elements, at least one of which is arranged to rotate relative to the other so that the refining surfaces may move in relation to one another. One refiner, however, may also comprise several pairs of opposing refining elements. There is a blade gap between the opposing refining elements, into which blade gap material to be refined is fed. The refining elements comprise one annular blade element or several sector-like blade elements providing together an annular refining element. The blade elements comprise blade bars and blade grooves therebetween, the blade bars and the blade grooves providing a refining surface of the blade element, whereby the refining surface of a single blade element alone or the refining surfaces of several blade elements provide a refining surface of the refining element. The blade elements are typically manufactured by casting a blade element billet, which comprises a blade element body and blade bar billets and blade groove billets therebetween, which blade bar billets and blade groove billets may thereafter be machined for finalizing the blade bar and blade groove geometry.
US publication 6616078 B1 discloses a blade element for a refiner for refining fibrous material. The blade element has blade bars and blade grooves therebetween. Bottoms of the blade grooves have, in the longitudinal direction of the blade grooves, a variable profile comprising alternating high points and low points. The variable profile of the bottom of the blade groove, comprising alternating high points and low points, forces the material to be refined to flow into the blade gap between the opposing refining elements. The purpose is to ensure that all the material fed into the refiner enters into the blade gap in order to be refined, whereby any portion of the material fed into the refiner would not just flow through the refiner without entering into the blade gap to be processed.